NEW YORK (Reuters Health) - Patients who report penicillin allergy face an increased risk of surgical-site infection (SSI), according to a retrospective study.

"I was surprised that the whole effect was mediated by antibiotic choice, which really speaks to a unique ability to make a meaningful change in surgical-site infection risk if we can change that antibiotic choice," Dr. Kimberly J. Blumenthal from Massachusetts General Hospital (MGH) and Harvard Medical School, in Boston, told Reuters Health by email.

Cefazolin, a first-generation cephalosporin antibiotic, is often used perioperatively to reduce SSI incidence, but in the presence of penicillin allergy, alternative antibiotics may be administered.

In all, 922 patients (11%) reporting a penicillin allergy had 1,042 documented reactions to penicillin, according to the October 9 Clinical Infectious Diseases online report.

Only 5 of those reactions (<0.5%) were likely to represent true contraindications to receiving beta-lactam antibiotics. The odds of SSI were 51% higher among patients reporting penicillin allergy than among those not reporting penicillin allergy.

Patients reporting penicillin allergy were significantly less likely than others to receive cefazolin - and more likely to receive clindamycin, vancomycin, gentamicin, and fluoroquinolones.

In a multivariable model, the effect of penicillin-allergy reporting on SSI development was entirely mediated through receipt of a beta-lactam alternative antibiotic. In effect, the greater likelihood of an SSI in patients with a reported penicillin allergy was wholly attributable to the alternative antibiotic used to prevent such infections.

To prevent one SSI, 112 to 124 patients with reported penicillin allergy would need an allergy evaluation.

"A surgical-site infection costs from $20,000 to $25,000," Dr. Blumenthal said. "The cost of penicillin allergy evaluation ranges from $40 to $1,247 depending on the evaluation type/complexity and costing method used. So, it is not clear yet if this is a cost-saving intervention, but it is likely be a cost-effective intervention under a wide range of assumptions."

"We'd hope that physicians consider that their patients labeled as penicillin-allergic may not be truly allergic, and consider how the mislabeling impacts care, especially for those with upcoming surgery," she said.

"It often takes more than one study to motivate widespread practice changes and/or guideline changes, but considering the morbidity of surgical-site infections and modest resources needed to clarify the allergy, I recommend penicillin-allergy evaluation in advance of surgical procedures to increase the chances of getting the recommended antibiotic," Dr. Blumenthal concluded.

Dr. Antonia F. Chen from Sidney Kimmel Medical College, Thomas Jefferson University Hospital, in Philadelphia, who recently studied vancomycin-only prophylaxis for patients with penicillin allergy undergoing arthroplasty, told Reuters Health by email, "Patients with a reported penicillin allergy should be screened to determine the extent to which a cephalosporin allergy may truly exist, if at all. In appropriate cases and in collaboration with our colleagues in anesthesia, we should consider administering cephalosporins prior to elective surgical procedures in the safety of a monitored environment to reduce the risk of SSI."

"It is expensive to test cross-reactivity in patients with a reported penicillin allergy, but a simple and quick questionnaire can provide a cost-effective method of screening patients for a valid cephalosporin allergy," she said. "Our institution developed a questionnaire to assess penicillin allergy based on reactions to specific medications (penicillin vs. cephalosporins), including the type of reaction; the age at the time of the reaction; the time frame between drug administration and symptoms; what happened when penicillin was discontinued; and whether or not a family history of the reported allergy exists."

"We concluded that only patients who experienced anaphylactic reactions to cephalosporins within the past 10 years should not receive such medications (e.g., cefazolin)," Dr. Chen said. "In other words, it is cost-effective to reduce the risk of SSI in just one patient compared to administering a simple questionnaire to 112 to 124 patients."